An F3C heli with 3D roots
This article was originally published in RC Heli Pilot February/March 2016 issue.
Words And Photos By Chuck Bassan
The rationale behind the original design of the Goblin Urukay was to produce a helicopter targeted towards F3C flying while also maintaining a quite capable 3D flight performance envelope. This ‘hybrid’ design ultimately proved to be quite successful and to date is very much in demand. On the heels of the original Goblin Urukay is the brand new Goblin Urukay Competition. Sporting some significant improvements, the Urukay Competition delivers some structural improvements, enhanced streamlining and an all-out increase in performance.
WEIGHT: (All electronics / without batteries): 10.0 lb. (4.5 kg)
LENGTH: 56.7 in. (1,440mm)
HEIGHT: 15.9 in. (405mm)
WIDTH: 7.3 in. (186mm)
ROTOR SPAN: (w/725mm blades) 64.5 in. (1,638 mm)
ROTOR DISK AREA: 3,265 sq. in. (2,106 sq. cm)
TAIL ROTOR DIAMETER: 12.0 in. (304mm)
MAIN BLADES: 725mm (included)
TAIL BLADES: 104mm (included)
MAIN ROTOR RPM AT HOVER: 1,700
DURATION: 5 – 10 minutes (depending on head-speed and flying style)
MINIMAL FLYING AREA: Club field
NEEDED TO COMPLETE: Radio system, swash servos (x3), tail servo, FBL controller, motor, ESC, BEC (if ESC doesn’t provide this feature), flight battery, radio battery (if not using BEC) and a radio battery backup (optional – but highly recommended).
• Comprehensive and well written instruction manual
• Exceptional parts quality (in both fit and finish)
• Beautifully finished canopy and tail boom
• Outstanding flight performance
• Relatively expensive
I’m not going to lie, I’m a big fan of Goblins, but I have good reason. They are fun to build, a breeze to set up and a pure pleasure to fly. Maintenance is minimal and parts availability is never an issue; the perfect recipe for a successful recreational activity. With regards to the Goblin Urukay Competition specifically, SAB has unquestionably stepped up their game. They have designed and implemented marked improvements on what I already thought was an industry leading platform. And oh yeah – have I mentioned that it is one beautiful looking bird?
I’d like to dive right into the meat of what sets the Urukay Competition apart from its predecessor. First and foremost, the Urukay Competition comes standard with the SAB high-performance HPS3 three-blade main rotor head and a matched set of SAB 725mm Black-Line main blades. The pitch arms on the main rotor grips have been moved further out in order to create a larger control radius, which directly translates into greater positioning resolution out of your flybarless controller. Working down from there, the three main blade pitch links now utilize Titanium turnbuckles, thus making tracking adjustments a breeze. For optimum gear mesh, the main gear is now CNC machined and runs true right from the get-go.
The ESC mounting platform has been moved up top, facilitating an extremely short wire run between the ESC and the motor. For enhanced heat-sinking properties, the ESC platform itself is machined out of solid aluminum and also features pre-drilled and tapped holes for hard mounting either a Kontronik Kosmik or YGE ESC. Of course any ESC can be used, but easily accommodating those two popular options are a nice touch. The battery compartment is cavernous and provides more than sufficient room to give you an option of
4 different battery mounting configurations. This is priceless for achieving an optimum CG. The kit also includes two removable battery trays as well as the heat-shrink necessary for constructing purpose built battery packs.
Even the tail boom saw significant improvements as it now completely seals off the rear end of the canopy. The tail rotor pitch control pushrod has been relocated inside the tail boom and the vertical fin is now an integral part of the tail boom – both aimed at streamlining the overall appearance of the heli. Even the tail rotor has been upgraded to a three-blade unit. Last but not least – the landing gear is now a one-piece conventional design. To sum it up, the Goblin Urukay is one beautifully executed piece of engineering. It is quite obvious that this model isn’t just another 3D machine with a pattern ship canopy slapped on it.
I LOVE building Goblins. By virtue of the exceptionally written manual and carefully labeled parts bags, the kit practically falls together. You’re going to be hard pressed to find a more satisfying build experience. One thing to note is that the manual suggests that there are two mounting locations for the battery support tray, however, the lower most position really isn’t available as the frame sides have been cut incorrectly for proper installation in that location. Having mentioned that, it doesn’t turn out to be an issue because even in the upper position there is sufficient space for any suitable battery packs.
Electronics placement has been thoughtfully laid out. As described earlier, the ESC is now located just in front of the motor. A few centimeters of wire are all that’s needed to connect the two. The front of the ESC also ends up right where the batteries protrude from the front of the frame, allowing you to keep those wires relatively short as well.
For routing the ESC signal and BEC wires to the rear of the frame, a carbon fiber plate has been added along the top-left side of the heli, offset out about 10mm from frame. This makes for a nice and tidy installation and appearance. The top-rear portion of the frame provides plenty of room for mounting your RX, FBL controller, BEC and a back-up guard. Another welcome modification to the Urukay Competition is the location of the tail pitch servo, which now rests on aluminum servo mounts located inside the frame.
IN THE AIR
I’m not a big fan of stick banging. I gravitate more towards precision flying and for my style of flying, the Goblin Urukay Competition is THE perfect heli. From the first flight, I knew this machine was destined to become one of my favorites. Hovering maneuvers look as if the model is just sitting on a pedestal and I know this is going to sound like an old worn out cliché, but this thing tracks like a bullet.
With the stock 20T pinion and the OS 520Kv motor, I’m getting 7+ minutes flights on 4500mAh packs running an 1850 RPM head speed. For hovering routines, I’m flying around at 1350 RPM and the heli sounds flies like it’s in stealth mode. Average motor amperage lingers at approximately 45A, with peaks hitting around 190 Amps when flying mild 3D.
Putting the Urukay through a series of F3C style pattern maneuvers, it is clear that this model does exactly what it is advertised to do. Tracking is spot on and when the radio and FBL systems are setup properly, the flight characteristics are beyond smooth. With the lower head speeds, the Urukay has no problem at all with 3D type maneuvers either; something to be said for the pop of a 3-blade head design.
Visibility is awesome. The red and white paint scheme really stands out. I generally seem to have minor visibility issues with red helicopters, but there’s something about this one that makes it just pop. Honestly, I can’t think of a single bad thing to say about the Urukay Competition’s flight performance. I love it.
Material: 2mm Carbon Fiber
Type: Carbon Fiber Plates, Aluminum Transmission Sub-Assembly and Spacers
Servo linkage type: Direct to Swash
Grips: Aluminum w/Replaceable Pitch Arms, Dual Radial / Single Thrust Bearing
Head block: Aluminum / Triple 10mm Spindles
Links: Plastic Links / Steel Balls – Titanium Turnbuckles on Main Blade Pitch Links
Swash Follower: Aluminum (integrated into head block)
Mainshaft: 12mm Hardened Steel (hollow)
Drive system: Toothed Belt
Auto Capable: Yes, tail driven auto-rotation capable Tail Pitch Slider Type: Aluminum Arms / Plastic Ring (on 6 mm tail rotor shaft)
Tail Blade Grips: Aluminum, Dual Radial / Single Thrust Bearing
Tail Case: Aluminum
Boom Material: Carbon Fiber
Tail Fin: Vertical Only (integrated with boom)
1. ESC mounted up-top, in close proximity to the motor for minimizing wire lengths. 2. HPS3 3-blade main rotor head.
3. Titanium turnbuckle pitch links.
4. CNC machined main gear.
5. Huge battery compartment.
6. One-piece conventional landing gear.
7. Integrated vertical fin.
8. Three-blade tail rotor.
9. Tail rotor pitch change push-rod is routed inside the tail boom.
Be careful when assembling the tail-rotor pitch change links. Do not over tighten them as they will surely bind. Use red, high- strength thread lock and check for smooth operation while tight- ening. Tighten until you feel binding and back-off until smooth operation is achieved.
The ESC / BEC lead runs are going to be quite long. Be sure to route them through a few turns of a ferrite donut in order to mini- mize the potential for electrical interference.
Use dry-lube on the CNC main gear.
THE LAST WORD
If you’re even thinking about giving F3C flying a go, it’s certainly worth giving the Goblin Urukay Competition some serious consideration. Why? Because it’s a stable platform for the precision maneuvers, tracks like a bullet for the big air routines and is more than capable of breaking out the 3D when its show-off time. I guarantee you’re going to love this machine.
SAB GOBLIN goblin-helicopter.com
ESPRIT MODEL espritmodel.com, (321) 729-4287
BAVARIAN DEMON bavariandemon.com
HITEC hitecrcd.com, (858) 748-6948
JETI MODEL jetimodel.com
O.S. ENGINES osengines.com, (217) 398-8970